Colours (Infantry) and Guidons (Cavalry) have their origin as markers or flags around which bodies of troops rallied. At the beginning they often bore the badge of their commander on a flag or colour made of the regiment's uniform facing colour. From the eighteenth century onwards (except for a short period when all English Regiments had white facings), both the Devonshires (11th Regiment of Foot) and the Dorsets (39th and 54th Regiments of Foot) had green facings and hence green colours.
Nowadays the infantry have two colours, a Regimental Colour, which is green in the case of the Devonshire and Dorset Regiment, and a Queen's Colour or Union Flag. The Queen's Own Dorset Yeomanry had a single Green Guidon of a smaller size, designed to be carried on horseback. The Dorset Yeomanry, now being only of squadron strength do not have an official issue Guidon but one of their own.
Badges and Battle Honours have been added to the Colours and to the Guidon to make them unique and revered memorials to the regiments and their achievements.